Refactor derived Generic instances to reduce allocations

Previously, derived implementations of `to`/`from` in `Generic`
instances were wastefully putting extra `M1`s in every case, which led
to an O(n) increase in the number of coercions, resulting in a slowdown
during the typechecker phase.

This factors out the common `M1` in every case of a `to`/`from`
definition so that the typechecker has far fewer coercions to deal with.
For a datatype with 300 constructors, this change has been observed to
save almost 3 seconds of compilation time.

This is one step towards coming up with a solution for #5642.

Test Plan: ./validate

Reviewers: hvr, austin, simonpj, bgamari

Reviewed By: bgamari

Subscribers: basvandijk, carter, thomie, osa1

Differential Revision: https://phabricator.haskell.org/D2304

GHC Trac Issues: #5642

7 files changed, 589 insertions, 547 deletions

diff --git a/testsuite/tests/generics/GenDerivOutput.stderr b/testsuite/tests/generics/GenDerivOutput.stderr
index de11f431e9..2226783029 100644
--- a/testsuite/tests/generics/GenDerivOutput.stderr
+++ b/testsuite/tests/generics/GenDerivOutput.stderr
@@ -2,92 +2,96 @@
 ==================== Derived instances ====================
 Derived instances:
   instance GHC.Generics.Generic (GenDerivOutput.List a) where
-    GHC.Generics.from GenDerivOutput.Nil
+    GHC.Generics.from x
       = GHC.Generics.M1
-          (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1))
-    GHC.Generics.from (GenDerivOutput.Cons g1 g2)
-      = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.K1 g2)))))
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)))
-      = GenDerivOutput.Nil
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                                                                             (GHC.Generics.M1 (GHC.Generics.K1 g2))))))
-      = GenDerivOutput.Cons g1 g2
-
+          (case x of {
+             GenDerivOutput.Nil
+               -> GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+             GenDerivOutput.Cons g1 g2
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.K1 g2)))) })
+    GHC.Generics.to (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+            -> GenDerivOutput.Nil
+          GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                                                               (GHC.Generics.M1 (GHC.Generics.K1 g2))))
+            -> GenDerivOutput.Cons g1 g2 }
+  
   instance GHC.Generics.Generic1 GenDerivOutput.List where
-    GHC.Generics.from1 GenDerivOutput.Nil
-      = GHC.Generics.M1
-          (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1))
-    GHC.Generics.from1 (GenDerivOutput.Cons g1 g2)
+    GHC.Generics.from1 x
       = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.Par1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.Rec1 g2)))))
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)))
-      = GenDerivOutput.Nil
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
-                                                                             (GHC.Generics.M1 g2)))))
-      = GenDerivOutput.Cons
-          (GHC.Generics.unPar1 g1) (GHC.Generics.unRec1 g2)
-
+          (case x of {
+             GenDerivOutput.Nil
+               -> GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+             GenDerivOutput.Cons g1 g2
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.Par1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.Rec1 g2)))) })
+    GHC.Generics.to1 (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+            -> GenDerivOutput.Nil
+          GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
+                                                               (GHC.Generics.M1 g2)))
+            -> GenDerivOutput.Cons
+                 (GHC.Generics.unPar1 g1) (GHC.Generics.unRec1 g2) }
+  
   instance GHC.Base.Functor GenDerivOutput.List where
     GHC.Base.fmap f GenDerivOutput.Nil = GenDerivOutput.Nil
     GHC.Base.fmap f (GenDerivOutput.Cons a1 a2)
       = GenDerivOutput.Cons (f a1) (GHC.Base.fmap f a2)
-
+  
   instance GHC.Generics.Generic (GenDerivOutput.Rose a) where
-    GHC.Generics.from GenDerivOutput.Empty
+    GHC.Generics.from x
       = GHC.Generics.M1
-          (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1))
-    GHC.Generics.from (GenDerivOutput.Rose g1 g2)
-      = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.K1 g2)))))
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)))
-      = GenDerivOutput.Empty
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                                                                             (GHC.Generics.M1 (GHC.Generics.K1 g2))))))
-      = GenDerivOutput.Rose g1 g2
-
+          (case x of {
+             GenDerivOutput.Empty
+               -> GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+             GenDerivOutput.Rose g1 g2
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.K1 g2)))) })
+    GHC.Generics.to (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+            -> GenDerivOutput.Empty
+          GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                                                               (GHC.Generics.M1 (GHC.Generics.K1 g2))))
+            -> GenDerivOutput.Rose g1 g2 }
+  
   instance GHC.Generics.Generic1 GenDerivOutput.Rose where
-    GHC.Generics.from1 GenDerivOutput.Empty
+    GHC.Generics.from1 x
       = GHC.Generics.M1
-          (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1))
-    GHC.Generics.from1 (GenDerivOutput.Rose g1 g2)
-      = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.Par1 g1))
-                   (GHC.Generics.M1
-                      ((GHC.Base..)
-                         GHC.Generics.Comp1 (GHC.Base.fmap GHC.Generics.Rec1) g2)))))
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)))
-      = GenDerivOutput.Empty
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
-                                                                             (GHC.Generics.M1 g2)))))
-      = GenDerivOutput.Rose
-          (GHC.Generics.unPar1 g1)
-          ((GHC.Base..)
-             (GHC.Base.fmap GHC.Generics.unRec1) GHC.Generics.unComp1 g2)
-
+          (case x of {
+             GenDerivOutput.Empty
+               -> GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+             GenDerivOutput.Rose g1 g2
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.Par1 g1))
+                          (GHC.Generics.M1
+                             ((GHC.Base..)
+                                GHC.Generics.Comp1 (GHC.Base.fmap GHC.Generics.Rec1) g2)))) })
+    GHC.Generics.to1 (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+            -> GenDerivOutput.Empty
+          GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
+                                                               (GHC.Generics.M1 g2)))
+            -> GenDerivOutput.Rose
+                 (GHC.Generics.unPar1 g1)
+                 ((GHC.Base..)
+                    (GHC.Base.fmap GHC.Generics.unRec1) GHC.Generics.unComp1 g2) }
+  
 
 GHC.Generics representation types:
   type GHC.Generics.Rep (GenDerivOutput.List a) = GHC.Generics.D1
diff --git a/testsuite/tests/generics/GenDerivOutput1_0.stderr b/testsuite/tests/generics/GenDerivOutput1_0.stderr
index 0f4df6275a..cc12b64a39 100644
--- a/testsuite/tests/generics/GenDerivOutput1_0.stderr
+++ b/testsuite/tests/generics/GenDerivOutput1_0.stderr
@@ -2,25 +2,26 @@
 ==================== Derived instances ====================
 Derived instances:
   instance GHC.Generics.Generic1 GenDerivOutput1_0.List where
-    GHC.Generics.from1 GenDerivOutput1_0.Nil
+    GHC.Generics.from1 x
       = GHC.Generics.M1
-          (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1))
-    GHC.Generics.from1 (GenDerivOutput1_0.Cons g1 g2)
-      = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.Par1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.Rec1 g2)))))
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)))
-      = GenDerivOutput1_0.Nil
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
-                                                                             (GHC.Generics.M1 g2)))))
-      = GenDerivOutput1_0.Cons
-          (GHC.Generics.unPar1 g1) (GHC.Generics.unRec1 g2)
-
+          (case x of {
+             GenDerivOutput1_0.Nil
+               -> GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+             GenDerivOutput1_0.Cons g1 g2
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.Par1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.Rec1 g2)))) })
+    GHC.Generics.to1 (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+            -> GenDerivOutput1_0.Nil
+          GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
+                                                               (GHC.Generics.M1 g2)))
+            -> GenDerivOutput1_0.Cons
+                 (GHC.Generics.unPar1 g1) (GHC.Generics.unRec1 g2) }
+  
 
 GHC.Generics representation types:
   type GHC.Generics.Rep1 GenDerivOutput1_0.List = GHC.Generics.D1
diff --git a/testsuite/tests/generics/GenDerivOutput1_1.stderr b/testsuite/tests/generics/GenDerivOutput1_1.stderr
index d76d6bb593..53dbda1d62 100644
--- a/testsuite/tests/generics/GenDerivOutput1_1.stderr
+++ b/testsuite/tests/generics/GenDerivOutput1_1.stderr
@@ -2,157 +2,165 @@
 ==================== Derived instances ====================
 Derived instances:
   instance GHC.Generics.Generic1 CanDoRep1_1.Dd where
-    GHC.Generics.from1 CanDoRep1_1.D0d
+    GHC.Generics.from1 x
       = GHC.Generics.M1
-          (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1))
-    GHC.Generics.from1 (CanDoRep1_1.D1d g1 g2)
-      = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.Par1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.Rec1 g2)))))
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)))
-      = CanDoRep1_1.D0d
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
-                                                                             (GHC.Generics.M1 g2)))))
-      = CanDoRep1_1.D1d (GHC.Generics.unPar1 g1) (GHC.Generics.unRec1 g2)
-
+          (case x of {
+             CanDoRep1_1.D0d
+               -> GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+             CanDoRep1_1.D1d g1 g2
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.Par1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.Rec1 g2)))) })
+    GHC.Generics.to1 (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+            -> CanDoRep1_1.D0d
+          GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
+                                                               (GHC.Generics.M1 g2)))
+            -> CanDoRep1_1.D1d
+                 (GHC.Generics.unPar1 g1) (GHC.Generics.unRec1 g2) }
+  
   instance GHC.Generics.Generic (CanDoRep1_1.Dd a) where
-    GHC.Generics.from CanDoRep1_1.D0d
+    GHC.Generics.from x
       = GHC.Generics.M1
-          (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1))
-    GHC.Generics.from (CanDoRep1_1.D1d g1 g2)
-      = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.K1 g2)))))
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)))
-      = CanDoRep1_1.D0d
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                                                                             (GHC.Generics.M1 (GHC.Generics.K1 g2))))))
-      = CanDoRep1_1.D1d g1 g2
-
+          (case x of {
+             CanDoRep1_1.D0d
+               -> GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+             CanDoRep1_1.D1d g1 g2
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.K1 g2)))) })
+    GHC.Generics.to (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+            -> CanDoRep1_1.D0d
+          GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                                                               (GHC.Generics.M1 (GHC.Generics.K1 g2))))
+            -> CanDoRep1_1.D1d g1 g2 }
+  
   instance GHC.Generics.Generic (CanDoRep1_1.Dc a) where
-    GHC.Generics.from CanDoRep1_1.D0c
+    GHC.Generics.from x
       = GHC.Generics.M1
-          (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1))
-    GHC.Generics.from (CanDoRep1_1.D1c g1 g2)
-      = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.K1 g2)))))
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)))
-      = CanDoRep1_1.D0c
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                                                                             (GHC.Generics.M1 (GHC.Generics.K1 g2))))))
-      = CanDoRep1_1.D1c g1 g2
-
+          (case x of {
+             CanDoRep1_1.D0c
+               -> GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+             CanDoRep1_1.D1c g1 g2
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.K1 g2)))) })
+    GHC.Generics.to (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+            -> CanDoRep1_1.D0c
+          GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                                                               (GHC.Generics.M1 (GHC.Generics.K1 g2))))
+            -> CanDoRep1_1.D1c g1 g2 }
+  
   instance GHC.Generics.Generic1 CanDoRep1_1.Db where
-    GHC.Generics.from1 CanDoRep1_1.D0b
+    GHC.Generics.from1 x
       = GHC.Generics.M1
-          (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1))
-    GHC.Generics.from1 (CanDoRep1_1.D1b g1 g2)
-      = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.Par1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.Rec1 g2)))))
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)))
-      = CanDoRep1_1.D0b
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
-                                                                             (GHC.Generics.M1 g2)))))
-      = CanDoRep1_1.D1b (GHC.Generics.unPar1 g1) (GHC.Generics.unRec1 g2)
-
+          (case x of {
+             CanDoRep1_1.D0b
+               -> GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+             CanDoRep1_1.D1b g1 g2
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.Par1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.Rec1 g2)))) })
+    GHC.Generics.to1 (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+            -> CanDoRep1_1.D0b
+          GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
+                                                               (GHC.Generics.M1 g2)))
+            -> CanDoRep1_1.D1b
+                 (GHC.Generics.unPar1 g1) (GHC.Generics.unRec1 g2) }
+  
   instance GHC.Generics.Generic (CanDoRep1_1.Da a) where
-    GHC.Generics.from CanDoRep1_1.D0
+    GHC.Generics.from x
       = GHC.Generics.M1
-          (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1))
-    GHC.Generics.from (CanDoRep1_1.D1 g1 g2)
-      = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.K1 g2)))))
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)))
-      = CanDoRep1_1.D0
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                                                                             (GHC.Generics.M1 (GHC.Generics.K1 g2))))))
-      = CanDoRep1_1.D1 g1 g2
-
+          (case x of {
+             CanDoRep1_1.D0 -> GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+             CanDoRep1_1.D1 g1 g2
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.K1 g2)))) })
+    GHC.Generics.to (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1) -> CanDoRep1_1.D0
+          GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                                                               (GHC.Generics.M1 (GHC.Generics.K1 g2))))
+            -> CanDoRep1_1.D1 g1 g2 }
+  
   instance GHC.Generics.Generic1 CanDoRep1_1.Da where
-    GHC.Generics.from1 CanDoRep1_1.D0
+    GHC.Generics.from1 x
       = GHC.Generics.M1
-          (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1))
-    GHC.Generics.from1 (CanDoRep1_1.D1 g1 g2)
-      = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.Par1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.Rec1 g2)))))
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)))
-      = CanDoRep1_1.D0
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
-                                                                             (GHC.Generics.M1 g2)))))
-      = CanDoRep1_1.D1 (GHC.Generics.unPar1 g1) (GHC.Generics.unRec1 g2)
-
+          (case x of {
+             CanDoRep1_1.D0 -> GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+             CanDoRep1_1.D1 g1 g2
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.Par1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.Rec1 g2)))) })
+    GHC.Generics.to1 (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1) -> CanDoRep1_1.D0
+          GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
+                                                               (GHC.Generics.M1 g2)))
+            -> CanDoRep1_1.D1
+                 (GHC.Generics.unPar1 g1) (GHC.Generics.unRec1 g2) }
+  
   instance GHC.Generics.Generic (CanDoRep1_1.Db a) where
-    GHC.Generics.from CanDoRep1_1.D0b
+    GHC.Generics.from x
       = GHC.Generics.M1
-          (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1))
-    GHC.Generics.from (CanDoRep1_1.D1b g1 g2)
-      = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.K1 g2)))))
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)))
-      = CanDoRep1_1.D0b
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                                                                             (GHC.Generics.M1 (GHC.Generics.K1 g2))))))
-      = CanDoRep1_1.D1b g1 g2
-
+          (case x of {
+             CanDoRep1_1.D0b
+               -> GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+             CanDoRep1_1.D1b g1 g2
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.K1 g2)))) })
+    GHC.Generics.to (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+            -> CanDoRep1_1.D0b
+          GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                                                               (GHC.Generics.M1 (GHC.Generics.K1 g2))))
+            -> CanDoRep1_1.D1b g1 g2 }
+  
   instance GHC.Generics.Generic1 CanDoRep1_1.Dc where
-    GHC.Generics.from1 CanDoRep1_1.D0c
+    GHC.Generics.from1 x
       = GHC.Generics.M1
-          (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1))
-    GHC.Generics.from1 (CanDoRep1_1.D1c g1 g2)
-      = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.Par1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.Rec1 g2)))))
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)))
-      = CanDoRep1_1.D0c
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
-                                                                             (GHC.Generics.M1 g2)))))
-      = CanDoRep1_1.D1c (GHC.Generics.unPar1 g1) (GHC.Generics.unRec1 g2)
-
+          (case x of {
+             CanDoRep1_1.D0c
+               -> GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+             CanDoRep1_1.D1c g1 g2
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.Par1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.Rec1 g2)))) })
+    GHC.Generics.to1 (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 GHC.Generics.U1)
+            -> CanDoRep1_1.D0c
+          GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
+                                                               (GHC.Generics.M1 g2)))
+            -> CanDoRep1_1.D1c
+                 (GHC.Generics.unPar1 g1) (GHC.Generics.unRec1 g2) }
+  
 
 GHC.Generics representation types:
   type GHC.Generics.Rep1 CanDoRep1_1.Dd = GHC.Generics.D1
diff --git a/testsuite/tests/generics/T10604/T10604_deriving.stderr b/testsuite/tests/generics/T10604/T10604_deriving.stderr
index cecb2ce308..cbaba8dbbe 100644
--- a/testsuite/tests/generics/T10604/T10604_deriving.stderr
+++ b/testsuite/tests/generics/T10604/T10604_deriving.stderr
@@ -2,162 +2,187 @@
 ==================== Derived instances ====================
 Derived instances:
   instance GHC.Generics.Generic (T10604_deriving.Empty a) where
-    GHC.Generics.from _
+    GHC.Generics.from x
       = GHC.Generics.M1
-          (GHC.Err.error
-             "No generic representation for empty datatype Empty")
-    GHC.Generics.to (GHC.Generics.M1 _)
-      = GHC.Err.error "No values for empty datatype Empty"
+          (case x of {
+             _ -> GHC.Err.error
+                    "No generic representation for empty datatype Empty" })
+    GHC.Generics.to (GHC.Generics.M1 x)
+      = case x of {
+          _ -> GHC.Err.error "No values for empty datatype Empty" }
   
   instance GHC.Generics.Generic1
              GHC.Types.Bool T10604_deriving.Empty where
-    GHC.Generics.from1 _
+    GHC.Generics.from1 x
       = GHC.Generics.M1
-          (GHC.Err.error
-             "No generic representation for empty datatype Empty")
-    GHC.Generics.to1 (GHC.Generics.M1 _)
-      = GHC.Err.error "No values for empty datatype Empty"
+          (case x of {
+             _ -> GHC.Err.error
+                    "No generic representation for empty datatype Empty" })
+    GHC.Generics.to1 (GHC.Generics.M1 x)
+      = case x of {
+          _ -> GHC.Err.error "No values for empty datatype Empty" }
   
   instance GHC.Base.Functor (T10604_deriving.Proxy *) where
     GHC.Base.fmap f T10604_deriving.Proxy = T10604_deriving.Proxy
   
   instance forall k (a :: k).
            GHC.Generics.Generic (T10604_deriving.Proxy k a) where
-    GHC.Generics.from T10604_deriving.Proxy
-      = GHC.Generics.M1 (GHC.Generics.M1 GHC.Generics.U1)
-    GHC.Generics.to (GHC.Generics.M1 (GHC.Generics.M1 GHC.Generics.U1))
-      = T10604_deriving.Proxy
+    GHC.Generics.from x
+      = GHC.Generics.M1
+          (case x of {
+             T10604_deriving.Proxy -> GHC.Generics.M1 GHC.Generics.U1 })
+    GHC.Generics.to (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.M1 GHC.Generics.U1 -> T10604_deriving.Proxy }
   
   instance GHC.Generics.Generic1 k (T10604_deriving.Proxy k) where
-    GHC.Generics.from1 T10604_deriving.Proxy
-      = GHC.Generics.M1 (GHC.Generics.M1 GHC.Generics.U1)
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.M1 GHC.Generics.U1))
-      = T10604_deriving.Proxy
+    GHC.Generics.from1 x
+      = GHC.Generics.M1
+          (case x of {
+             T10604_deriving.Proxy -> GHC.Generics.M1 GHC.Generics.U1 })
+    GHC.Generics.to1 (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.M1 GHC.Generics.U1 -> T10604_deriving.Proxy }
   
   instance GHC.Generics.Generic (T10604_deriving.Wrap a) where
-    GHC.Generics.from (T10604_deriving.Wrap g1)
+    GHC.Generics.from x
       = GHC.Generics.M1
-          (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1)))
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1))))
-      = T10604_deriving.Wrap g1
+          (case x of {
+             T10604_deriving.Wrap g1
+               -> GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1)) })
+    GHC.Generics.to (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1))
+            -> T10604_deriving.Wrap g1 }
   
   instance GHC.Generics.Generic1
              (GHC.Types.* -> GHC.Types.*) T10604_deriving.Wrap where
-    GHC.Generics.from1 (T10604_deriving.Wrap g1)
+    GHC.Generics.from1 x
       = GHC.Generics.M1
-          (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.Rec1 g1)))
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.M1 g1)))
-      = T10604_deriving.Wrap (GHC.Generics.unRec1 g1)
+          (case x of {
+             T10604_deriving.Wrap g1
+               -> GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.Rec1 g1)) })
+    GHC.Generics.to1 (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.M1 (GHC.Generics.M1 g1)
+            -> T10604_deriving.Wrap (GHC.Generics.unRec1 g1) }
   
   instance forall k (a :: k -> GHC.Types.*).
            GHC.Generics.Generic (T10604_deriving.Wrap2 k a) where
-    GHC.Generics.from (T10604_deriving.Wrap2 g1)
+    GHC.Generics.from x
       = GHC.Generics.M1
-          (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1)))
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1))))
-      = T10604_deriving.Wrap2 g1
+          (case x of {
+             T10604_deriving.Wrap2 g1
+               -> GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1)) })
+    GHC.Generics.to (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1))
+            -> T10604_deriving.Wrap2 g1 }
   
   instance GHC.Generics.Generic1
              (k -> GHC.Types.*) (T10604_deriving.Wrap2 k) where
-    GHC.Generics.from1 (T10604_deriving.Wrap2 g1)
+    GHC.Generics.from1 x
       = GHC.Generics.M1
-          (GHC.Generics.M1
-             (GHC.Generics.M1
-                ((GHC.Base..)
-                   GHC.Generics.Comp1 (GHC.Base.fmap GHC.Generics.Rec1) g1)))
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.M1 g1)))
-      = T10604_deriving.Wrap2
-          ((GHC.Base..)
-             (GHC.Base.fmap GHC.Generics.unRec1) GHC.Generics.unComp1 g1)
+          (case x of {
+             T10604_deriving.Wrap2 g1
+               -> GHC.Generics.M1
+                    (GHC.Generics.M1
+                       ((GHC.Base..)
+                          GHC.Generics.Comp1 (GHC.Base.fmap GHC.Generics.Rec1) g1)) })
+    GHC.Generics.to1 (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.M1 (GHC.Generics.M1 g1)
+            -> T10604_deriving.Wrap2
+                 ((GHC.Base..)
+                    (GHC.Base.fmap GHC.Generics.unRec1) GHC.Generics.unComp1 g1) }
   
   instance forall k (a :: k).
            GHC.Generics.Generic (T10604_deriving.SumOfProducts k a) where
-    GHC.Generics.from (T10604_deriving.Prod1 g1 g2)
-      = GHC.Generics.M1
-          (GHC.Generics.L1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.K1 g2)))))
-    GHC.Generics.from (T10604_deriving.Prod2 g1 g2)
+    GHC.Generics.from x
       = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.K1 g2)))))
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                                                                             (GHC.Generics.M1 (GHC.Generics.K1 g2))))))
-      = T10604_deriving.Prod1 g1 g2
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
-                                                                             (GHC.Generics.M1 (GHC.Generics.K1 g2))))))
-      = T10604_deriving.Prod2 g1 g2
+          (case x of {
+             T10604_deriving.Prod1 g1 g2
+               -> GHC.Generics.L1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.K1 g2))))
+             T10604_deriving.Prod2 g1 g2
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.K1 g2)))) })
+    GHC.Generics.to (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                                                               (GHC.Generics.M1 (GHC.Generics.K1 g2))))
+            -> T10604_deriving.Prod1 g1 g2
+          GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 (GHC.Generics.K1 g1))
+                                                               (GHC.Generics.M1 (GHC.Generics.K1 g2))))
+            -> T10604_deriving.Prod2 g1 g2 }
   
   instance GHC.Generics.Generic1
              k (T10604_deriving.SumOfProducts k) where
-    GHC.Generics.from1 (T10604_deriving.Prod1 g1 g2)
+    GHC.Generics.from1 x
       = GHC.Generics.M1
-          (GHC.Generics.L1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.Rec1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.Rec1 g2)))))
-    GHC.Generics.from1 (T10604_deriving.Prod2 g1 g2)
-      = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1
-                ((GHC.Generics.:*:)
-                   (GHC.Generics.M1 (GHC.Generics.Rec1 g1))
-                   (GHC.Generics.M1 (GHC.Generics.Rec1 g2)))))
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
-                                                                             (GHC.Generics.M1 g2)))))
-      = T10604_deriving.Prod1
-          (GHC.Generics.unRec1 g1) (GHC.Generics.unRec1 g2)
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
-                                                                             (GHC.Generics.M1 g2)))))
-      = T10604_deriving.Prod2
-          (GHC.Generics.unRec1 g1) (GHC.Generics.unRec1 g2)
+          (case x of {
+             T10604_deriving.Prod1 g1 g2
+               -> GHC.Generics.L1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.Rec1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.Rec1 g2))))
+             T10604_deriving.Prod2 g1 g2
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1
+                       ((GHC.Generics.:*:)
+                          (GHC.Generics.M1 (GHC.Generics.Rec1 g1))
+                          (GHC.Generics.M1 (GHC.Generics.Rec1 g2)))) })
+    GHC.Generics.to1 (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
+                                                               (GHC.Generics.M1 g2)))
+            -> T10604_deriving.Prod1
+                 (GHC.Generics.unRec1 g1) (GHC.Generics.unRec1 g2)
+          GHC.Generics.R1 (GHC.Generics.M1 ((GHC.Generics.:*:) (GHC.Generics.M1 g1)
+                                                               (GHC.Generics.M1 g2)))
+            -> T10604_deriving.Prod2
+                 (GHC.Generics.unRec1 g1) (GHC.Generics.unRec1 g2) }
   
   instance GHC.Generics.Generic (T10604_deriving.Starify a) where
-    GHC.Generics.from (T10604_deriving.Starify1 g1)
-      = GHC.Generics.M1
-          (GHC.Generics.L1
-             (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1))))
-    GHC.Generics.from (T10604_deriving.Starify2 g1)
+    GHC.Generics.from x
       = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1))))
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1)))))
-      = T10604_deriving.Starify1 g1
-    GHC.Generics.to
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1)))))
-      = T10604_deriving.Starify2 g1
+          (case x of {
+             T10604_deriving.Starify1 g1
+               -> GHC.Generics.L1
+                    (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1)))
+             T10604_deriving.Starify2 g1
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1))) })
+    GHC.Generics.to (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1)))
+            -> T10604_deriving.Starify1 g1
+          GHC.Generics.R1 (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1)))
+            -> T10604_deriving.Starify2 g1 }
   
   instance GHC.Generics.Generic1 * T10604_deriving.Starify where
-    GHC.Generics.from1 (T10604_deriving.Starify1 g1)
-      = GHC.Generics.M1
-          (GHC.Generics.L1
-             (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.Par1 g1))))
-    GHC.Generics.from1 (T10604_deriving.Starify2 g1)
+    GHC.Generics.from1 x
       = GHC.Generics.M1
-          (GHC.Generics.R1
-             (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1))))
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.L1 (GHC.Generics.M1 (GHC.Generics.M1 g1))))
-      = T10604_deriving.Starify1 (GHC.Generics.unPar1 g1)
-    GHC.Generics.to1
-      (GHC.Generics.M1 (GHC.Generics.R1 (GHC.Generics.M1 (GHC.Generics.M1 g1))))
-      = T10604_deriving.Starify2 (GHC.Generics.unK1 g1)
+          (case x of {
+             T10604_deriving.Starify1 g1
+               -> GHC.Generics.L1
+                    (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.Par1 g1)))
+             T10604_deriving.Starify2 g1
+               -> GHC.Generics.R1
+                    (GHC.Generics.M1 (GHC.Generics.M1 (GHC.Generics.K1 g1))) })
+    GHC.Generics.to1 (GHC.Generics.M1 x)
+      = case x of {
+          GHC.Generics.L1 (GHC.Generics.M1 (GHC.Generics.M1 g1))
+            -> T10604_deriving.Starify1 (GHC.Generics.unPar1 g1)
+          GHC.Generics.R1 (GHC.Generics.M1 (GHC.Generics.M1 g1))
+            -> T10604_deriving.Starify2 (GHC.Generics.unK1 g1) }
   
 
 GHC.Generics representation types:
diff --git a/testsuite/tests/perf/compiler/T5642.hs b/testsuite/tests/perf/compiler/T5642.hs
index 00c7ee012c..cc4a98026b 100644
--- a/testsuite/tests/perf/compiler/T5642.hs
+++ b/testsuite/tests/perf/compiler/T5642.hs
@@ -44,206 +44,208 @@ module GenBigTypes where
 
   instance Generic BigSum where
     type Rep BigSum = Rep_BigSum
-    from C0 = M1 (L1 (L1 (L1 (L1 (L1 (L1 (M1 U1)))))))
-    from C1 = M1 (L1 (L1 (L1 (L1 (L1 (R1 (L1 (M1 U1))))))))
-    from C2 = M1 (L1 (L1 (L1 (L1 (L1 (R1 (R1 (M1 U1))))))))
-    from C3 = M1 (L1 (L1 (L1 (L1 (R1 (L1 (M1 U1)))))))
-    from C4 = M1 (L1 (L1 (L1 (L1 (R1 (R1 (L1 (M1 U1))))))))
-    from C5 = M1 (L1 (L1 (L1 (L1 (R1 (R1 (R1 (M1 U1))))))))
-    from C6 = M1 (L1 (L1 (L1 (R1 (L1 (L1 (M1 U1)))))))
-    from C7 = M1 (L1 (L1 (L1 (R1 (L1 (R1 (L1 (M1 U1))))))))
-    from C8 = M1 (L1 (L1 (L1 (R1 (L1 (R1 (R1 (M1 U1))))))))
-    from C9 = M1 (L1 (L1 (L1 (R1 (R1 (L1 (M1 U1)))))))
-    from C10 = M1 (L1 (L1 (L1 (R1 (R1 (R1 (L1 (M1 U1))))))))
-    from C11 = M1 (L1 (L1 (L1 (R1 (R1 (R1 (R1 (M1 U1))))))))
-    from C12 = M1 (L1 (L1 (R1 (L1 (L1 (L1 (M1 U1)))))))
-    from C13 = M1 (L1 (L1 (R1 (L1 (L1 (R1 (L1 (M1 U1))))))))
-    from C14 = M1 (L1 (L1 (R1 (L1 (L1 (R1 (R1 (M1 U1))))))))
-    from C15 = M1 (L1 (L1 (R1 (L1 (R1 (L1 (M1 U1)))))))
-    from C16 = M1 (L1 (L1 (R1 (L1 (R1 (R1 (L1 (M1 U1))))))))
-    from C17 = M1 (L1 (L1 (R1 (L1 (R1 (R1 (R1 (M1 U1))))))))
-    from C18 = M1 (L1 (L1 (R1 (R1 (L1 (L1 (M1 U1)))))))
-    from C19 = M1 (L1 (L1 (R1 (R1 (L1 (R1 (L1 (M1 U1))))))))
-    from C20 = M1 (L1 (L1 (R1 (R1 (L1 (R1 (R1 (M1 U1))))))))
-    from C21 = M1 (L1 (L1 (R1 (R1 (R1 (L1 (L1 (M1 U1))))))))
-    from C22 = M1 (L1 (L1 (R1 (R1 (R1 (L1 (R1 (M1 U1))))))))
-    from C23 = M1 (L1 (L1 (R1 (R1 (R1 (R1 (L1 (M1 U1))))))))
-    from C24 = M1 (L1 (L1 (R1 (R1 (R1 (R1 (R1 (M1 U1))))))))
-    from C25 = M1 (L1 (R1 (L1 (L1 (L1 (L1 (M1 U1)))))))
-    from C26 = M1 (L1 (R1 (L1 (L1 (L1 (R1 (L1 (M1 U1))))))))
-    from C27 = M1 (L1 (R1 (L1 (L1 (L1 (R1 (R1 (M1 U1))))))))
-    from C28 = M1 (L1 (R1 (L1 (L1 (R1 (L1 (M1 U1)))))))
-    from C29 = M1 (L1 (R1 (L1 (L1 (R1 (R1 (L1 (M1 U1))))))))
-    from C30 = M1 (L1 (R1 (L1 (L1 (R1 (R1 (R1 (M1 U1))))))))
-    from C31 = M1 (L1 (R1 (L1 (R1 (L1 (L1 (M1 U1)))))))
-    from C32 = M1 (L1 (R1 (L1 (R1 (L1 (R1 (L1 (M1 U1))))))))
-    from C33 = M1 (L1 (R1 (L1 (R1 (L1 (R1 (R1 (M1 U1))))))))
-    from C34 = M1 (L1 (R1 (L1 (R1 (R1 (L1 (M1 U1)))))))
-    from C35 = M1 (L1 (R1 (L1 (R1 (R1 (R1 (L1 (M1 U1))))))))
-    from C36 = M1 (L1 (R1 (L1 (R1 (R1 (R1 (R1 (M1 U1))))))))
-    from C37 = M1 (L1 (R1 (R1 (L1 (L1 (L1 (M1 U1)))))))
-    from C38 = M1 (L1 (R1 (R1 (L1 (L1 (R1 (L1 (M1 U1))))))))
-    from C39 = M1 (L1 (R1 (R1 (L1 (L1 (R1 (R1 (M1 U1))))))))
-    from C40 = M1 (L1 (R1 (R1 (L1 (R1 (L1 (M1 U1)))))))
-    from C41 = M1 (L1 (R1 (R1 (L1 (R1 (R1 (L1 (M1 U1))))))))
-    from C42 = M1 (L1 (R1 (R1 (L1 (R1 (R1 (R1 (M1 U1))))))))
-    from C43 = M1 (L1 (R1 (R1 (R1 (L1 (L1 (M1 U1)))))))
-    from C44 = M1 (L1 (R1 (R1 (R1 (L1 (R1 (L1 (M1 U1))))))))
-    from C45 = M1 (L1 (R1 (R1 (R1 (L1 (R1 (R1 (M1 U1))))))))
-    from C46 = M1 (L1 (R1 (R1 (R1 (R1 (L1 (L1 (M1 U1))))))))
-    from C47 = M1 (L1 (R1 (R1 (R1 (R1 (L1 (R1 (M1 U1))))))))
-    from C48 = M1 (L1 (R1 (R1 (R1 (R1 (R1 (L1 (M1 U1))))))))
-    from C49 = M1 (L1 (R1 (R1 (R1 (R1 (R1 (R1 (M1 U1))))))))
-    from C50 = M1 (R1 (L1 (L1 (L1 (L1 (L1 (M1 U1)))))))
-    from C51 = M1 (R1 (L1 (L1 (L1 (L1 (R1 (L1 (M1 U1))))))))
-    from C52 = M1 (R1 (L1 (L1 (L1 (L1 (R1 (R1 (M1 U1))))))))
-    from C53 = M1 (R1 (L1 (L1 (L1 (R1 (L1 (M1 U1)))))))
-    from C54 = M1 (R1 (L1 (L1 (L1 (R1 (R1 (L1 (M1 U1))))))))
-    from C55 = M1 (R1 (L1 (L1 (L1 (R1 (R1 (R1 (M1 U1))))))))
-    from C56 = M1 (R1 (L1 (L1 (R1 (L1 (L1 (M1 U1)))))))
-    from C57 = M1 (R1 (L1 (L1 (R1 (L1 (R1 (L1 (M1 U1))))))))
-    from C58 = M1 (R1 (L1 (L1 (R1 (L1 (R1 (R1 (M1 U1))))))))
-    from C59 = M1 (R1 (L1 (L1 (R1 (R1 (L1 (M1 U1)))))))
-    from C60 = M1 (R1 (L1 (L1 (R1 (R1 (R1 (L1 (M1 U1))))))))
-    from C61 = M1 (R1 (L1 (L1 (R1 (R1 (R1 (R1 (M1 U1))))))))
-    from C62 = M1 (R1 (L1 (R1 (L1 (L1 (L1 (M1 U1)))))))
-    from C63 = M1 (R1 (L1 (R1 (L1 (L1 (R1 (L1 (M1 U1))))))))
-    from C64 = M1 (R1 (L1 (R1 (L1 (L1 (R1 (R1 (M1 U1))))))))
-    from C65 = M1 (R1 (L1 (R1 (L1 (R1 (L1 (M1 U1)))))))
-    from C66 = M1 (R1 (L1 (R1 (L1 (R1 (R1 (L1 (M1 U1))))))))
-    from C67 = M1 (R1 (L1 (R1 (L1 (R1 (R1 (R1 (M1 U1))))))))
-    from C68 = M1 (R1 (L1 (R1 (R1 (L1 (L1 (M1 U1)))))))
-    from C69 = M1 (R1 (L1 (R1 (R1 (L1 (R1 (L1 (M1 U1))))))))
-    from C70 = M1 (R1 (L1 (R1 (R1 (L1 (R1 (R1 (M1 U1))))))))
-    from C71 = M1 (R1 (L1 (R1 (R1 (R1 (L1 (L1 (M1 U1))))))))
-    from C72 = M1 (R1 (L1 (R1 (R1 (R1 (L1 (R1 (M1 U1))))))))
-    from C73 = M1 (R1 (L1 (R1 (R1 (R1 (R1 (L1 (M1 U1))))))))
-    from C74 = M1 (R1 (L1 (R1 (R1 (R1 (R1 (R1 (M1 U1))))))))
-    from C75 = M1 (R1 (R1 (L1 (L1 (L1 (L1 (M1 U1)))))))
-    from C76 = M1 (R1 (R1 (L1 (L1 (L1 (R1 (L1 (M1 U1))))))))
-    from C77 = M1 (R1 (R1 (L1 (L1 (L1 (R1 (R1 (M1 U1))))))))
-    from C78 = M1 (R1 (R1 (L1 (L1 (R1 (L1 (M1 U1)))))))
-    from C79 = M1 (R1 (R1 (L1 (L1 (R1 (R1 (L1 (M1 U1))))))))
-    from C80 = M1 (R1 (R1 (L1 (L1 (R1 (R1 (R1 (M1 U1))))))))
-    from C81 = M1 (R1 (R1 (L1 (R1 (L1 (L1 (M1 U1)))))))
-    from C82 = M1 (R1 (R1 (L1 (R1 (L1 (R1 (L1 (M1 U1))))))))
-    from C83 = M1 (R1 (R1 (L1 (R1 (L1 (R1 (R1 (M1 U1))))))))
-    from C84 = M1 (R1 (R1 (L1 (R1 (R1 (L1 (M1 U1)))))))
-    from C85 = M1 (R1 (R1 (L1 (R1 (R1 (R1 (L1 (M1 U1))))))))
-    from C86 = M1 (R1 (R1 (L1 (R1 (R1 (R1 (R1 (M1 U1))))))))
-    from C87 = M1 (R1 (R1 (R1 (L1 (L1 (L1 (M1 U1)))))))
-    from C88 = M1 (R1 (R1 (R1 (L1 (L1 (R1 (L1 (M1 U1))))))))
-    from C89 = M1 (R1 (R1 (R1 (L1 (L1 (R1 (R1 (M1 U1))))))))
-    from C90 = M1 (R1 (R1 (R1 (L1 (R1 (L1 (M1 U1)))))))
-    from C91 = M1 (R1 (R1 (R1 (L1 (R1 (R1 (L1 (M1 U1))))))))
-    from C92 = M1 (R1 (R1 (R1 (L1 (R1 (R1 (R1 (M1 U1))))))))
-    from C93 = M1 (R1 (R1 (R1 (R1 (L1 (L1 (M1 U1)))))))
-    from C94 = M1 (R1 (R1 (R1 (R1 (L1 (R1 (L1 (M1 U1))))))))
-    from C95 = M1 (R1 (R1 (R1 (R1 (L1 (R1 (R1 (M1 U1))))))))
-    from C96 = M1 (R1 (R1 (R1 (R1 (R1 (L1 (L1 (M1 U1))))))))
-    from C97 = M1 (R1 (R1 (R1 (R1 (R1 (L1 (R1 (M1 U1))))))))
-    from C98 = M1 (R1 (R1 (R1 (R1 (R1 (R1 (L1 (M1 U1))))))))
-    from C99 = M1 (R1 (R1 (R1 (R1 (R1 (R1 (R1 (M1 U1))))))))
-    to (M1 (L1 (L1 (L1 (L1 (L1 (L1 (M1 U1)))))))) = C0
-    to (M1 (L1 (L1 (L1 (L1 (L1 (R1 (L1 (M1 U1))))))))) = C1
-    to (M1 (L1 (L1 (L1 (L1 (L1 (R1 (R1 (M1 U1))))))))) = C2
-    to (M1 (L1 (L1 (L1 (L1 (R1 (L1 (M1 U1)))))))) = C3
-    to (M1 (L1 (L1 (L1 (L1 (R1 (R1 (L1 (M1 U1))))))))) = C4
-    to (M1 (L1 (L1 (L1 (L1 (R1 (R1 (R1 (M1 U1))))))))) = C5
-    to (M1 (L1 (L1 (L1 (R1 (L1 (L1 (M1 U1)))))))) = C6
-    to (M1 (L1 (L1 (L1 (R1 (L1 (R1 (L1 (M1 U1))))))))) = C7
-    to (M1 (L1 (L1 (L1 (R1 (L1 (R1 (R1 (M1 U1))))))))) = C8
-    to (M1 (L1 (L1 (L1 (R1 (R1 (L1 (M1 U1)))))))) = C9
-    to (M1 (L1 (L1 (L1 (R1 (R1 (R1 (L1 (M1 U1))))))))) = C10
-    to (M1 (L1 (L1 (L1 (R1 (R1 (R1 (R1 (M1 U1))))))))) = C11
-    to (M1 (L1 (L1 (R1 (L1 (L1 (L1 (M1 U1)))))))) = C12
-    to (M1 (L1 (L1 (R1 (L1 (L1 (R1 (L1 (M1 U1))))))))) = C13
-    to (M1 (L1 (L1 (R1 (L1 (L1 (R1 (R1 (M1 U1))))))))) = C14
-    to (M1 (L1 (L1 (R1 (L1 (R1 (L1 (M1 U1)))))))) = C15
-    to (M1 (L1 (L1 (R1 (L1 (R1 (R1 (L1 (M1 U1))))))))) = C16
-    to (M1 (L1 (L1 (R1 (L1 (R1 (R1 (R1 (M1 U1))))))))) = C17
-    to (M1 (L1 (L1 (R1 (R1 (L1 (L1 (M1 U1)))))))) = C18
-    to (M1 (L1 (L1 (R1 (R1 (L1 (R1 (L1 (M1 U1))))))))) = C19
-    to (M1 (L1 (L1 (R1 (R1 (L1 (R1 (R1 (M1 U1))))))))) = C20
-    to (M1 (L1 (L1 (R1 (R1 (R1 (L1 (L1 (M1 U1))))))))) = C21
-    to (M1 (L1 (L1 (R1 (R1 (R1 (L1 (R1 (M1 U1))))))))) = C22
-    to (M1 (L1 (L1 (R1 (R1 (R1 (R1 (L1 (M1 U1))))))))) = C23
-    to (M1 (L1 (L1 (R1 (R1 (R1 (R1 (R1 (M1 U1))))))))) = C24
-    to (M1 (L1 (R1 (L1 (L1 (L1 (L1 (M1 U1)))))))) = C25
-    to (M1 (L1 (R1 (L1 (L1 (L1 (R1 (L1 (M1 U1))))))))) = C26
-    to (M1 (L1 (R1 (L1 (L1 (L1 (R1 (R1 (M1 U1))))))))) = C27
-    to (M1 (L1 (R1 (L1 (L1 (R1 (L1 (M1 U1)))))))) = C28
-    to (M1 (L1 (R1 (L1 (L1 (R1 (R1 (L1 (M1 U1))))))))) = C29
-    to (M1 (L1 (R1 (L1 (L1 (R1 (R1 (R1 (M1 U1))))))))) = C30
-    to (M1 (L1 (R1 (L1 (R1 (L1 (L1 (M1 U1)))))))) = C31
-    to (M1 (L1 (R1 (L1 (R1 (L1 (R1 (L1 (M1 U1))))))))) = C32
-    to (M1 (L1 (R1 (L1 (R1 (L1 (R1 (R1 (M1 U1))))))))) = C33
-    to (M1 (L1 (R1 (L1 (R1 (R1 (L1 (M1 U1)))))))) = C34
-    to (M1 (L1 (R1 (L1 (R1 (R1 (R1 (L1 (M1 U1))))))))) = C35
-    to (M1 (L1 (R1 (L1 (R1 (R1 (R1 (R1 (M1 U1))))))))) = C36
-    to (M1 (L1 (R1 (R1 (L1 (L1 (L1 (M1 U1)))))))) = C37
-    to (M1 (L1 (R1 (R1 (L1 (L1 (R1 (L1 (M1 U1))))))))) = C38
-    to (M1 (L1 (R1 (R1 (L1 (L1 (R1 (R1 (M1 U1))))))))) = C39
-    to (M1 (L1 (R1 (R1 (L1 (R1 (L1 (M1 U1)))))))) = C40
-    to (M1 (L1 (R1 (R1 (L1 (R1 (R1 (L1 (M1 U1))))))))) = C41
-    to (M1 (L1 (R1 (R1 (L1 (R1 (R1 (R1 (M1 U1))))))))) = C42
-    to (M1 (L1 (R1 (R1 (R1 (L1 (L1 (M1 U1)))))))) = C43
-    to (M1 (L1 (R1 (R1 (R1 (L1 (R1 (L1 (M1 U1))))))))) = C44
-    to (M1 (L1 (R1 (R1 (R1 (L1 (R1 (R1 (M1 U1))))))))) = C45
-    to (M1 (L1 (R1 (R1 (R1 (R1 (L1 (L1 (M1 U1))))))))) = C46
-    to (M1 (L1 (R1 (R1 (R1 (R1 (L1 (R1 (M1 U1))))))))) = C47
-    to (M1 (L1 (R1 (R1 (R1 (R1 (R1 (L1 (M1 U1))))))))) = C48
-    to (M1 (L1 (R1 (R1 (R1 (R1 (R1 (R1 (M1 U1))))))))) = C49
-    to (M1 (R1 (L1 (L1 (L1 (L1 (L1 (M1 U1)))))))) = C50
-    to (M1 (R1 (L1 (L1 (L1 (L1 (R1 (L1 (M1 U1))))))))) = C51
-    to (M1 (R1 (L1 (L1 (L1 (L1 (R1 (R1 (M1 U1))))))))) = C52
-    to (M1 (R1 (L1 (L1 (L1 (R1 (L1 (M1 U1)))))))) = C53
-    to (M1 (R1 (L1 (L1 (L1 (R1 (R1 (L1 (M1 U1))))))))) = C54
-    to (M1 (R1 (L1 (L1 (L1 (R1 (R1 (R1 (M1 U1))))))))) = C55
-    to (M1 (R1 (L1 (L1 (R1 (L1 (L1 (M1 U1)))))))) = C56
-    to (M1 (R1 (L1 (L1 (R1 (L1 (R1 (L1 (M1 U1))))))))) = C57
-    to (M1 (R1 (L1 (L1 (R1 (L1 (R1 (R1 (M1 U1))))))))) = C58
-    to (M1 (R1 (L1 (L1 (R1 (R1 (L1 (M1 U1)))))))) = C59
-    to (M1 (R1 (L1 (L1 (R1 (R1 (R1 (L1 (M1 U1))))))))) = C60
-    to (M1 (R1 (L1 (L1 (R1 (R1 (R1 (R1 (M1 U1))))))))) = C61
-    to (M1 (R1 (L1 (R1 (L1 (L1 (L1 (M1 U1)))))))) = C62
-    to (M1 (R1 (L1 (R1 (L1 (L1 (R1 (L1 (M1 U1))))))))) = C63
-    to (M1 (R1 (L1 (R1 (L1 (L1 (R1 (R1 (M1 U1))))))))) = C64
-    to (M1 (R1 (L1 (R1 (L1 (R1 (L1 (M1 U1)))))))) = C65
-    to (M1 (R1 (L1 (R1 (L1 (R1 (R1 (L1 (M1 U1))))))))) = C66
-    to (M1 (R1 (L1 (R1 (L1 (R1 (R1 (R1 (M1 U1))))))))) = C67
-    to (M1 (R1 (L1 (R1 (R1 (L1 (L1 (M1 U1)))))))) = C68
-    to (M1 (R1 (L1 (R1 (R1 (L1 (R1 (L1 (M1 U1))))))))) = C69
-    to (M1 (R1 (L1 (R1 (R1 (L1 (R1 (R1 (M1 U1))))))))) = C70
-    to (M1 (R1 (L1 (R1 (R1 (R1 (L1 (L1 (M1 U1))))))))) = C71
-    to (M1 (R1 (L1 (R1 (R1 (R1 (L1 (R1 (M1 U1))))))))) = C72
-    to (M1 (R1 (L1 (R1 (R1 (R1 (R1 (L1 (M1 U1))))))))) = C73
-    to (M1 (R1 (L1 (R1 (R1 (R1 (R1 (R1 (M1 U1))))))))) = C74
-    to (M1 (R1 (R1 (L1 (L1 (L1 (L1 (M1 U1)))))))) = C75
-    to (M1 (R1 (R1 (L1 (L1 (L1 (R1 (L1 (M1 U1))))))))) = C76
-    to (M1 (R1 (R1 (L1 (L1 (L1 (R1 (R1 (M1 U1))))))))) = C77
-    to (M1 (R1 (R1 (L1 (L1 (R1 (L1 (M1 U1)))))))) = C78
-    to (M1 (R1 (R1 (L1 (L1 (R1 (R1 (L1 (M1 U1))))))))) = C79
-    to (M1 (R1 (R1 (L1 (L1 (R1 (R1 (R1 (M1 U1))))))))) = C80
-    to (M1 (R1 (R1 (L1 (R1 (L1 (L1 (M1 U1)))))))) = C81
-    to (M1 (R1 (R1 (L1 (R1 (L1 (R1 (L1 (M1 U1))))))))) = C82
-    to (M1 (R1 (R1 (L1 (R1 (L1 (R1 (R1 (M1 U1))))))))) = C83
-    to (M1 (R1 (R1 (L1 (R1 (R1 (L1 (M1 U1)))))))) = C84
-    to (M1 (R1 (R1 (L1 (R1 (R1 (R1 (L1 (M1 U1))))))))) = C85
-    to (M1 (R1 (R1 (L1 (R1 (R1 (R1 (R1 (M1 U1))))))))) = C86
-    to (M1 (R1 (R1 (R1 (L1 (L1 (L1 (M1 U1)))))))) = C87
-    to (M1 (R1 (R1 (R1 (L1 (L1 (R1 (L1 (M1 U1))))))))) = C88
-    to (M1 (R1 (R1 (R1 (L1 (L1 (R1 (R1 (M1 U1))))))))) = C89
-    to (M1 (R1 (R1 (R1 (L1 (R1 (L1 (M1 U1)))))))) = C90
-    to (M1 (R1 (R1 (R1 (L1 (R1 (R1 (L1 (M1 U1))))))))) = C91
-    to (M1 (R1 (R1 (R1 (L1 (R1 (R1 (R1 (M1 U1))))))))) = C92
-    to (M1 (R1 (R1 (R1 (R1 (L1 (L1 (M1 U1)))))))) = C93
-    to (M1 (R1 (R1 (R1 (R1 (L1 (R1 (L1 (M1 U1))))))))) = C94
-    to (M1 (R1 (R1 (R1 (R1 (L1 (R1 (R1 (M1 U1))))))))) = C95
-    to (M1 (R1 (R1 (R1 (R1 (R1 (L1 (L1 (M1 U1))))))))) = C96
-    to (M1 (R1 (R1 (R1 (R1 (R1 (L1 (R1 (M1 U1))))))))) = C97
-    to (M1 (R1 (R1 (R1 (R1 (R1 (R1 (L1 (M1 U1))))))))) = C98
-    to (M1 (R1 (R1 (R1 (R1 (R1 (R1 (R1 (M1 U1))))))))) = C99
+    from x = M1 (case x of
+      C0  -> L1 (L1 (L1 (L1 (L1 (L1 (M1 U1))))))
+      C1  -> L1 (L1 (L1 (L1 (L1 (R1 (L1 (M1 U1)))))))
+      C2  -> L1 (L1 (L1 (L1 (L1 (R1 (R1 (M1 U1)))))))
+      C3  -> L1 (L1 (L1 (L1 (R1 (L1 (M1 U1))))))
+      C4  -> L1 (L1 (L1 (L1 (R1 (R1 (L1 (M1 U1)))))))
+      C5  -> L1 (L1 (L1 (L1 (R1 (R1 (R1 (M1 U1)))))))
+      C6  -> L1 (L1 (L1 (R1 (L1 (L1 (M1 U1))))))
+      C7  -> L1 (L1 (L1 (R1 (L1 (R1 (L1 (M1 U1)))))))
+      C8  -> L1 (L1 (L1 (R1 (L1 (R1 (R1 (M1 U1)))))))
+      C9  -> L1 (L1 (L1 (R1 (R1 (L1 (M1 U1))))))
+      C10 -> L1 (L1 (L1 (R1 (R1 (R1 (L1 (M1 U1)))))))
+      C11 -> L1 (L1 (L1 (R1 (R1 (R1 (R1 (M1 U1)))))))
+      C12 -> L1 (L1 (R1 (L1 (L1 (L1 (M1 U1))))))
+      C13 -> L1 (L1 (R1 (L1 (L1 (R1 (L1 (M1 U1)))))))
+      C14 -> L1 (L1 (R1 (L1 (L1 (R1 (R1 (M1 U1)))))))
+      C15 -> L1 (L1 (R1 (L1 (R1 (L1 (M1 U1))))))
+      C16 -> L1 (L1 (R1 (L1 (R1 (R1 (L1 (M1 U1)))))))
+      C17 -> L1 (L1 (R1 (L1 (R1 (R1 (R1 (M1 U1)))))))
+      C18 -> L1 (L1 (R1 (R1 (L1 (L1 (M1 U1))))))
+      C19 -> L1 (L1 (R1 (R1 (L1 (R1 (L1 (M1 U1)))))))
+      C20 -> L1 (L1 (R1 (R1 (L1 (R1 (R1 (M1 U1)))))))
+      C21 -> L1 (L1 (R1 (R1 (R1 (L1 (L1 (M1 U1)))))))
+      C22 -> L1 (L1 (R1 (R1 (R1 (L1 (R1 (M1 U1)))))))
+      C23 -> L1 (L1 (R1 (R1 (R1 (R1 (L1 (M1 U1)))))))
+      C24 -> L1 (L1 (R1 (R1 (R1 (R1 (R1 (M1 U1)))))))
+      C25 -> L1 (R1 (L1 (L1 (L1 (L1 (M1 U1))))))
+      C26 -> L1 (R1 (L1 (L1 (L1 (R1 (L1 (M1 U1)))))))
+      C27 -> L1 (R1 (L1 (L1 (L1 (R1 (R1 (M1 U1)))))))
+      C28 -> L1 (R1 (L1 (L1 (R1 (L1 (M1 U1))))))
+      C29 -> L1 (R1 (L1 (L1 (R1 (R1 (L1 (M1 U1)))))))
+      C30 -> L1 (R1 (L1 (L1 (R1 (R1 (R1 (M1 U1)))))))
+      C31 -> L1 (R1 (L1 (R1 (L1 (L1 (M1 U1))))))
+      C32 -> L1 (R1 (L1 (R1 (L1 (R1 (L1 (M1 U1)))))))
+      C33 -> L1 (R1 (L1 (R1 (L1 (R1 (R1 (M1 U1)))))))
+      C34 -> L1 (R1 (L1 (R1 (R1 (L1 (M1 U1))))))
+      C35 -> L1 (R1 (L1 (R1 (R1 (R1 (L1 (M1 U1)))))))
+      C36 -> L1 (R1 (L1 (R1 (R1 (R1 (R1 (M1 U1)))))))
+      C37 -> L1 (R1 (R1 (L1 (L1 (L1 (M1 U1))))))
+      C38 -> L1 (R1 (R1 (L1 (L1 (R1 (L1 (M1 U1)))))))
+      C39 -> L1 (R1 (R1 (L1 (L1 (R1 (R1 (M1 U1)))))))
+      C40 -> L1 (R1 (R1 (L1 (R1 (L1 (M1 U1))))))
+      C41 -> L1 (R1 (R1 (L1 (R1 (R1 (L1 (M1 U1)))))))
+      C42 -> L1 (R1 (R1 (L1 (R1 (R1 (R1 (M1 U1)))))))
+      C43 -> L1 (R1 (R1 (R1 (L1 (L1 (M1 U1))))))
+      C44 -> L1 (R1 (R1 (R1 (L1 (R1 (L1 (M1 U1)))))))
+      C45 -> L1 (R1 (R1 (R1 (L1 (R1 (R1 (M1 U1)))))))
+      C46 -> L1 (R1 (R1 (R1 (R1 (L1 (L1 (M1 U1)))))))
+      C47 -> L1 (R1 (R1 (R1 (R1 (L1 (R1 (M1 U1)))))))
+      C48 -> L1 (R1 (R1 (R1 (R1 (R1 (L1 (M1 U1)))))))
+      C49 -> L1 (R1 (R1 (R1 (R1 (R1 (R1 (M1 U1)))))))
+      C50 -> R1 (L1 (L1 (L1 (L1 (L1 (M1 U1))))))
+      C51 -> R1 (L1 (L1 (L1 (L1 (R1 (L1 (M1 U1)))))))
+      C52 -> R1 (L1 (L1 (L1 (L1 (R1 (R1 (M1 U1)))))))
+      C53 -> R1 (L1 (L1 (L1 (R1 (L1 (M1 U1))))))
+      C54 -> R1 (L1 (L1 (L1 (R1 (R1 (L1 (M1 U1)))))))
+      C55 -> R1 (L1 (L1 (L1 (R1 (R1 (R1 (M1 U1)))))))
+      C56 -> R1 (L1 (L1 (R1 (L1 (L1 (M1 U1))))))
+      C57 -> R1 (L1 (L1 (R1 (L1 (R1 (L1 (M1 U1)))))))
+      C58 -> R1 (L1 (L1 (R1 (L1 (R1 (R1 (M1 U1)))))))
+      C59 -> R1 (L1 (L1 (R1 (R1 (L1 (M1 U1))))))
+      C60 -> R1 (L1 (L1 (R1 (R1 (R1 (L1 (M1 U1)))))))
+      C61 -> R1 (L1 (L1 (R1 (R1 (R1 (R1 (M1 U1)))))))
+      C62 -> R1 (L1 (R1 (L1 (L1 (L1 (M1 U1))))))
+      C63 -> R1 (L1 (R1 (L1 (L1 (R1 (L1 (M1 U1)))))))
+      C64 -> R1 (L1 (R1 (L1 (L1 (R1 (R1 (M1 U1)))))))
+      C65 -> R1 (L1 (R1 (L1 (R1 (L1 (M1 U1))))))
+      C66 -> R1 (L1 (R1 (L1 (R1 (R1 (L1 (M1 U1)))))))
+      C67 -> R1 (L1 (R1 (L1 (R1 (R1 (R1 (M1 U1)))))))
+      C68 -> R1 (L1 (R1 (R1 (L1 (L1 (M1 U1))))))
+      C69 -> R1 (L1 (R1 (R1 (L1 (R1 (L1 (M1 U1)))))))
+      C70 -> R1 (L1 (R1 (R1 (L1 (R1 (R1 (M1 U1)))))))
+      C71 -> R1 (L1 (R1 (R1 (R1 (L1 (L1 (M1 U1)))))))
+      C72 -> R1 (L1 (R1 (R1 (R1 (L1 (R1 (M1 U1)))))))
+      C73 -> R1 (L1 (R1 (R1 (R1 (R1 (L1 (M1 U1)))))))
+      C74 -> R1 (L1 (R1 (R1 (R1 (R1 (R1 (M1 U1)))))))
+      C75 -> R1 (R1 (L1 (L1 (L1 (L1 (M1 U1))))))
+      C76 -> R1 (R1 (L1 (L1 (L1 (R1 (L1 (M1 U1)))))))
+      C77 -> R1 (R1 (L1 (L1 (L1 (R1 (R1 (M1 U1)))))))
+      C78 -> R1 (R1 (L1 (L1 (R1 (L1 (M1 U1))))))
+      C79 -> R1 (R1 (L1 (L1 (R1 (R1 (L1 (M1 U1)))))))
+      C80 -> R1 (R1 (L1 (L1 (R1 (R1 (R1 (M1 U1)))))))
+      C81 -> R1 (R1 (L1 (R1 (L1 (L1 (M1 U1))))))
+      C82 -> R1 (R1 (L1 (R1 (L1 (R1 (L1 (M1 U1)))))))
+      C83 -> R1 (R1 (L1 (R1 (L1 (R1 (R1 (M1 U1)))))))
+      C84 -> R1 (R1 (L1 (R1 (R1 (L1 (M1 U1))))))
+      C85 -> R1 (R1 (L1 (R1 (R1 (R1 (L1 (M1 U1)))))))
+      C86 -> R1 (R1 (L1 (R1 (R1 (R1 (R1 (M1 U1)))))))
+      C87 -> R1 (R1 (R1 (L1 (L1 (L1 (M1 U1))))))
+      C88 -> R1 (R1 (R1 (L1 (L1 (R1 (L1 (M1 U1)))))))
+      C89 -> R1 (R1 (R1 (L1 (L1 (R1 (R1 (M1 U1)))))))
+      C90 -> R1 (R1 (R1 (L1 (R1 (L1 (M1 U1))))))
+      C91 -> R1 (R1 (R1 (L1 (R1 (R1 (L1 (M1 U1)))))))
+      C92 -> R1 (R1 (R1 (L1 (R1 (R1 (R1 (M1 U1)))))))
+      C93 -> R1 (R1 (R1 (R1 (L1 (L1 (M1 U1))))))
+      C94 -> R1 (R1 (R1 (R1 (L1 (R1 (L1 (M1 U1)))))))
+      C95 -> R1 (R1 (R1 (R1 (L1 (R1 (R1 (M1 U1)))))))
+      C96 -> R1 (R1 (R1 (R1 (R1 (L1 (L1 (M1 U1)))))))
+      C97 -> R1 (R1 (R1 (R1 (R1 (L1 (R1 (M1 U1)))))))
+      C98 -> R1 (R1 (R1 (R1 (R1 (R1 (L1 (M1 U1)))))))
+      C99 -> R1 (R1 (R1 (R1 (R1 (R1 (R1 (M1 U1))))))))
+    to (M1 x) = case x of
+      L1 (L1 (L1 (L1 (L1 (L1 (M1 U1)))))) -> C0
+      L1 (L1 (L1 (L1 (L1 (R1 (L1 (M1 U1))))))) -> C1
+      L1 (L1 (L1 (L1 (L1 (R1 (R1 (M1 U1))))))) -> C2
+      L1 (L1 (L1 (L1 (R1 (L1 (M1 U1)))))) -> C3
+      L1 (L1 (L1 (L1 (R1 (R1 (L1 (M1 U1))))))) -> C4
+      L1 (L1 (L1 (L1 (R1 (R1 (R1 (M1 U1))))))) -> C5
+      L1 (L1 (L1 (R1 (L1 (L1 (M1 U1)))))) -> C6
+      L1 (L1 (L1 (R1 (L1 (R1 (L1 (M1 U1))))))) -> C7
+      L1 (L1 (L1 (R1 (L1 (R1 (R1 (M1 U1))))))) -> C8
+      L1 (L1 (L1 (R1 (R1 (L1 (M1 U1)))))) -> C9
+      L1 (L1 (L1 (R1 (R1 (R1 (L1 (M1 U1))))))) -> C10
+      L1 (L1 (L1 (R1 (R1 (R1 (R1 (M1 U1))))))) -> C11
+      L1 (L1 (R1 (L1 (L1 (L1 (M1 U1)))))) -> C12
+      L1 (L1 (R1 (L1 (L1 (R1 (L1 (M1 U1))))))) -> C13
+      L1 (L1 (R1 (L1 (L1 (R1 (R1 (M1 U1))))))) -> C14
+      L1 (L1 (R1 (L1 (R1 (L1 (M1 U1)))))) -> C15
+      L1 (L1 (R1 (L1 (R1 (R1 (L1 (M1 U1))))))) -> C16
+      L1 (L1 (R1 (L1 (R1 (R1 (R1 (M1 U1))))))) -> C17
+      L1 (L1 (R1 (R1 (L1 (L1 (M1 U1)))))) -> C18
+      L1 (L1 (R1 (R1 (L1 (R1 (L1 (M1 U1))))))) -> C19
+      L1 (L1 (R1 (R1 (L1 (R1 (R1 (M1 U1))))))) -> C20
+      L1 (L1 (R1 (R1 (R1 (L1 (L1 (M1 U1))))))) -> C21
+      L1 (L1 (R1 (R1 (R1 (L1 (R1 (M1 U1))))))) -> C22
+      L1 (L1 (R1 (R1 (R1 (R1 (L1 (M1 U1))))))) -> C23
+      L1 (L1 (R1 (R1 (R1 (R1 (R1 (M1 U1))))))) -> C24
+      L1 (R1 (L1 (L1 (L1 (L1 (M1 U1)))))) -> C25
+      L1 (R1 (L1 (L1 (L1 (R1 (L1 (M1 U1))))))) -> C26
+      L1 (R1 (L1 (L1 (L1 (R1 (R1 (M1 U1))))))) -> C27
+      L1 (R1 (L1 (L1 (R1 (L1 (M1 U1)))))) -> C28
+      L1 (R1 (L1 (L1 (R1 (R1 (L1 (M1 U1))))))) -> C29
+      L1 (R1 (L1 (L1 (R1 (R1 (R1 (M1 U1))))))) -> C30
+      L1 (R1 (L1 (R1 (L1 (L1 (M1 U1)))))) -> C31
+      L1 (R1 (L1 (R1 (L1 (R1 (L1 (M1 U1))))))) -> C32
+      L1 (R1 (L1 (R1 (L1 (R1 (R1 (M1 U1))))))) -> C33
+      L1 (R1 (L1 (R1 (R1 (L1 (M1 U1)))))) -> C34
+      L1 (R1 (L1 (R1 (R1 (R1 (L1 (M1 U1))))))) -> C35
+      L1 (R1 (L1 (R1 (R1 (R1 (R1 (M1 U1))))))) -> C36
+      L1 (R1 (R1 (L1 (L1 (L1 (M1 U1)))))) -> C37
+      L1 (R1 (R1 (L1 (L1 (R1 (L1 (M1 U1))))))) -> C38
+      L1 (R1 (R1 (L1 (L1 (R1 (R1 (M1 U1))))))) -> C39
+      L1 (R1 (R1 (L1 (R1 (L1 (M1 U1)))))) -> C40
+      L1 (R1 (R1 (L1 (R1 (R1 (L1 (M1 U1))))))) -> C41
+      L1 (R1 (R1 (L1 (R1 (R1 (R1 (M1 U1))))))) -> C42
+      L1 (R1 (R1 (R1 (L1 (L1 (M1 U1)))))) -> C43
+      L1 (R1 (R1 (R1 (L1 (R1 (L1 (M1 U1))))))) -> C44
+      L1 (R1 (R1 (R1 (L1 (R1 (R1 (M1 U1))))))) -> C45
+      L1 (R1 (R1 (R1 (R1 (L1 (L1 (M1 U1))))))) -> C46
+      L1 (R1 (R1 (R1 (R1 (L1 (R1 (M1 U1))))))) -> C47
+      L1 (R1 (R1 (R1 (R1 (R1 (L1 (M1 U1))))))) -> C48
+      L1 (R1 (R1 (R1 (R1 (R1 (R1 (M1 U1))))))) -> C49
+      R1 (L1 (L1 (L1 (L1 (L1 (M1 U1)))))) -> C50
+      R1 (L1 (L1 (L1 (L1 (R1 (L1 (M1 U1))))))) -> C51
+      R1 (L1 (L1 (L1 (L1 (R1 (R1 (M1 U1))))))) -> C52
+      R1 (L1 (L1 (L1 (R1 (L1 (M1 U1)))))) -> C53
+      R1 (L1 (L1 (L1 (R1 (R1 (L1 (M1 U1))))))) -> C54
+      R1 (L1 (L1 (L1 (R1 (R1 (R1 (M1 U1))))))) -> C55
+      R1 (L1 (L1 (R1 (L1 (L1 (M1 U1)))))) -> C56
+      R1 (L1 (L1 (R1 (L1 (R1 (L1 (M1 U1))))))) -> C57
+      R1 (L1 (L1 (R1 (L1 (R1 (R1 (M1 U1))))))) -> C58
+      R1 (L1 (L1 (R1 (R1 (L1 (M1 U1)))))) -> C59
+      R1 (L1 (L1 (R1 (R1 (R1 (L1 (M1 U1))))))) -> C60
+      R1 (L1 (L1 (R1 (R1 (R1 (R1 (M1 U1))))))) -> C61
+      R1 (L1 (R1 (L1 (L1 (L1 (M1 U1)))))) -> C62
+      R1 (L1 (R1 (L1 (L1 (R1 (L1 (M1 U1))))))) -> C63
+      R1 (L1 (R1 (L1 (L1 (R1 (R1 (M1 U1))))))) -> C64
+      R1 (L1 (R1 (L1 (R1 (L1 (M1 U1)))))) -> C65
+      R1 (L1 (R1 (L1 (R1 (R1 (L1 (M1 U1))))))) -> C66
+      R1 (L1 (R1 (L1 (R1 (R1 (R1 (M1 U1))))))) -> C67
+      R1 (L1 (R1 (R1 (L1 (L1 (M1 U1)))))) -> C68
+      R1 (L1 (R1 (R1 (L1 (R1 (L1 (M1 U1))))))) -> C69
+      R1 (L1 (R1 (R1 (L1 (R1 (R1 (M1 U1))))))) -> C70
+      R1 (L1 (R1 (R1 (R1 (L1 (L1 (M1 U1))))))) -> C71
+      R1 (L1 (R1 (R1 (R1 (L1 (R1 (M1 U1))))))) -> C72
+      R1 (L1 (R1 (R1 (R1 (R1 (L1 (M1 U1))))))) -> C73
+      R1 (L1 (R1 (R1 (R1 (R1 (R1 (M1 U1))))))) -> C74
+      R1 (R1 (L1 (L1 (L1 (L1 (M1 U1)))))) -> C75
+      R1 (R1 (L1 (L1 (L1 (R1 (L1 (M1 U1))))))) -> C76
+      R1 (R1 (L1 (L1 (L1 (R1 (R1 (M1 U1))))))) -> C77
+      R1 (R1 (L1 (L1 (R1 (L1 (M1 U1)))))) -> C78
+      R1 (R1 (L1 (L1 (R1 (R1 (L1 (M1 U1))))))) -> C79
+      R1 (R1 (L1 (L1 (R1 (R1 (R1 (M1 U1))))))) -> C80
+      R1 (R1 (L1 (R1 (L1 (L1 (M1 U1)))))) -> C81
+      R1 (R1 (L1 (R1 (L1 (R1 (L1 (M1 U1))))))) -> C82
+      R1 (R1 (L1 (R1 (L1 (R1 (R1 (M1 U1))))))) -> C83
+      R1 (R1 (L1 (R1 (R1 (L1 (M1 U1)))))) -> C84
+      R1 (R1 (L1 (R1 (R1 (R1 (L1 (M1 U1))))))) -> C85
+      R1 (R1 (L1 (R1 (R1 (R1 (R1 (M1 U1))))))) -> C86
+      R1 (R1 (R1 (L1 (L1 (L1 (M1 U1)))))) -> C87
+      R1 (R1 (R1 (L1 (L1 (R1 (L1 (M1 U1))))))) -> C88
+      R1 (R1 (R1 (L1 (L1 (R1 (R1 (M1 U1))))))) -> C89
+      R1 (R1 (R1 (L1 (R1 (L1 (M1 U1)))))) -> C90
+      R1 (R1 (R1 (L1 (R1 (R1 (L1 (M1 U1))))))) -> C91
+      R1 (R1 (R1 (L1 (R1 (R1 (R1 (M1 U1))))))) -> C92
+      R1 (R1 (R1 (R1 (L1 (L1 (M1 U1)))))) -> C93
+      R1 (R1 (R1 (R1 (L1 (R1 (L1 (M1 U1))))))) -> C94
+      R1 (R1 (R1 (R1 (L1 (R1 (R1 (M1 U1))))))) -> C95
+      R1 (R1 (R1 (R1 (R1 (L1 (L1 (M1 U1))))))) -> C96
+      R1 (R1 (R1 (R1 (R1 (L1 (R1 (M1 U1))))))) -> C97
+      R1 (R1 (R1 (R1 (R1 (R1 (L1 (M1 U1))))))) -> C98
+      R1 (R1 (R1 (R1 (R1 (R1 (R1 (M1 U1))))))) -> C99
 
   type Rep_BigSum = D1
                                        ('MetaData
diff --git a/testsuite/tests/perf/compiler/all.T b/testsuite/tests/perf/compiler/all.T
index a09499915a..230cff5ac8 100644
--- a/testsuite/tests/perf/compiler/all.T
+++ b/testsuite/tests/perf/compiler/all.T
@@ -545,7 +545,7 @@ test('T5642',
             # 2014-12-10:  641085256 Improvements in constraints solver
             # 2016-04-06:  462677300
 
-            (wordsize(64), 1300685592, 10)])
+            (wordsize(64),  916484672, 10)])
             # prev:        1300000000
             # 2014-07-17:  1358833928 (general round of updates)
             # 2014-08-07:  1402242360 (caused by 1fc60ea)
@@ -558,8 +558,9 @@ test('T5642',
             # 2014-12-10:  1282916024 Improvements in constraints solver
             # 2015-10-28:  1412808976 Emit Typeable at definition site
             # 2015-11-22:  1071915072 Use TypeLits in the metadata encoding
-            # 2016-02-08:  950004816  Pattern match checker re-rework
+            # 2016-02-08:   950004816 Pattern match checker re-rework
             # 2016-05-12:  1300685592 Make Generic1 poly-kinded
+            # 2016-06-05:   916484672 Refactor derived Generic instances to reduce allocations
       ],
       compile,['-O'])
 
diff --git a/testsuite/tests/perf/haddock/all.T b/testsuite/tests/perf/haddock/all.T
index 3160a8a1e4..3f4926a8f9 100644
--- a/testsuite/tests/perf/haddock/all.T
+++ b/testsuite/tests/perf/haddock/all.T
@@ -52,7 +52,7 @@ test('haddock.base',
 test('haddock.Cabal',
      [unless(in_tree_compiler(), skip), req_haddock
      ,stats_num_field('bytes allocated',
-          [(wordsize(64), 11805238152, 5)
+          [(wordsize(64), 10997887320, 5)
             # 2012-08-14: 3255435248 (amd64/Linux)
             # 2012-08-29: 3324606664 (amd64/Linux, new codegen)
             # 2012-10-08: 3373401360 (amd64/Linux)
@@ -81,6 +81,7 @@ test('haddock.Cabal',
             # 2016-04-06: 11542374816 (amd64/Linux) - CSE improvements and others
             # 2016-04-07: 10963514352 (amd64/Linux) - Revert to what phabricator claims
             # 2016-05-22: 11805238152 (amd64/Linux) - Make Generic1 poly-kinded
+            # 2016-06-05: 10997887320 (amd64/Linux) - Refactor derived Generic instances to reduce allocations
 
           ,(platform('i386-unknown-mingw32'), 3293415576, 5)
             # 2012-10-30:                     1733638168 (x86/Windows)
@@ -88,7 +89,7 @@ test('haddock.Cabal',
             # 2014-01-28:                     1966911336 (x86/Windows)
             # 2014-04-24:                     2052220292 (x86/Windows)
             # 2014-12-01:                     3088635556 (x86/Windows)
-            # 2015-01-20:                     3293415576 
+            # 2015-01-20:                     3293415576
 
           ,(wordsize(32), 6268156056, 5)])
             # 2012-08-14: 1648610180 (x86/OSX)